Typically, thermoplastic synthetic resin has the characteristic that, when it is heated, the molecular bonding thereof breaks and thus it dissolves while becoming fluid to thereby be capable of changing the shape thereof, and also when the heated resin is cooled, it may be hardened and re-shaped, thus enabling the recycling thereof. Recently in the fields of protective cases for sports and various home appliances, a variety of shock-proof cushioning products resulting from binding thermoplastic synthetic resin molded products with fabric have been introduced.
A representative method for binding the thermoplastic synthetic resin molded product with the fabric is use of an adhesive. Although this method is very simple and may be easily performed by anyone, it suffers from complicated working processes, high defective rates and environmental pollution, and thus its application range becomes narrow. As alternatives thereto, Japanese Patent Application Publication No. 1997-001586 and Korean Patent Application Publication No. 2002-0042559 disclose a method of integrating a fabric with a thermoplastic synthetic resin material using a mold.
This method includes preparing a mold having a cavity corresponding to the shape of a final product, placing a fabric on the cavity of the mold, closing the mold, and filling a space between the fabric and the cavity of the mold with a molten thermoplastic synthetic resin material so that the fabric and the synthetic resin material are integrated. Briefly, this method is performed in such a manner that a thermoplastic synthetic resin material is injected into the cooled mold, and advantageously enables mass production of molded products in the shape of the cavity of the mold.
However, this method is problematic because the fluid thermoplastic synthetic resin maintained at a predetermined temperature or more is injected into the mold maintained at a relatively low temperature and then undergoes cold molding in the shape of the cavity of the mold, undesirably causing defects where the cavity of the mold is not fully filled with the molten thermoplastic synthetic resin or where the resin is excessively injected into the mold such that it overflows the cavity of the mold. Moreover, final products are defective to the extent that they cannot be restored, and hence, solutions thereto are urgently required.